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mac80211: Reject malformed SSID elements

PATCH In review Will Deacon 2 participants 4 messages Oct 4, 2019

Subsystems (3)
Stable branch mac80211 802.11 (including cfg80211/NL80211)
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Will Deacon

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#0 lore raw

PATCH 1/2 mac80211: Reject malformed SSID elements

Although this shouldn't occur in practice, it's a good idea to bounds check the length field of the SSID element prior to using it for things like allocations or memcpy operations.

Cc <[email protected]>
Cc Johannes Berg <[email protected]>
Cc Kees Cook <[email protected]>
Reported-by Nicolas Waisman <[email protected]>
Signed-off-by Will Deacon <[email protected]>
---
 net/mac80211/mlme.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
net/mac80211/mlme.c +3 -2
index 26a2f49208b6..54dd8849d1cc 100644
@@ -2633,7 +2633,8 @@ struct sk_buff *ieee80211_ap_probereq_get(struct ieee80211_hw *hw,
 
 	rcu_read_lock();
 	ssid = ieee80211_bss_get_ie(cbss, WLAN_EID_SSID);
-	if (WARN_ON_ONCE(ssid == NULL))
+	if (WARN_ONCE(!ssid || ssid[1] > IEEE80211_MAX_SSID_LEN,
+		      "invalid SSID element (len=%d)", ssid ? ssid[1] : -1))
 		ssid_len = 0;
 	else
 		ssid_len = ssid[1];

@@ -5233,7 +5234,7 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
 
 	rcu_read_lock();
 	ssidie = ieee80211_bss_get_ie(req->bss, WLAN_EID_SSID);
-	if (!ssidie) {
+	if (!ssidie || ssidie[1] > sizeof(assoc_data->ssid)) {
 		rcu_read_unlock();
 		kfree(assoc_data);
 		return -EINVAL;
Signature · 1 line
2.23.0.581.g78d2f28ef7-goog
author
#1 lore raw

PATCH 2/2 cfg80211: wext: Reject malformed SSID elements

Ensure the SSID element is bounds-checked prior to invoking memcpy() with its length field.

Cc <[email protected]>
Cc Johannes Berg <[email protected]>
Cc Kees Cook <[email protected]>
Reported-by Nicolas Waisman <[email protected]>
Signed-off-by Will Deacon <[email protected]>
---
 net/wireless/wext-sme.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
net/wireless/wext-sme.c +6 -2
index c67d7a82ab13..3fd2cc7fc36a 100644
@@ -201,6 +201,7 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 			       struct iw_request_info *info,
 			       struct iw_point *data, char *ssid)
 {
+	int ret = 0;
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
 
 	/* call only for station! */

@@ -219,7 +220,10 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 		if (ie) {
 			data->flags = 1;
 			data->length = ie[1];
-			memcpy(ssid, ie + 2, data->length);
+			if (data->length > IW_ESSID_MAX_SIZE)
+				ret = -EINVAL;
+			else
+				memcpy(ssid, ie + 2, data->length);
 		}
 		rcu_read_unlock();
 	} else if (wdev->wext.connect.ssid && wdev->wext.connect.ssid_len) {

@@ -229,7 +233,7 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 	}
 	wdev_unlock(wdev);
 
-	return 0;
+	return ret;
 }
 
 int cfg80211_mgd_wext_siwap(struct net_device *dev,
Signature · 1 line
2.23.0.581.g78d2f28ef7-goog
Reviewed-by on v1 2/2
#2 lore raw

Re: [PATCH 2/2] cfg80211: wext: Reject malformed SSID elements

Quoted 8 lines · Will Deacon

Ensure the SSID element is bounds-checked prior to invoking memcpy() with its length field.

Cc <[email protected]>
Cc Johannes Berg <[email protected]>
Cc Kees Cook <[email protected]>
Reported-by Nicolas Waisman <[email protected]>
Signed-off-by Will Deacon <[email protected]>
Reviewed-by Kees Cook <[email protected]>

-Kees

Quoted 40 lines
---
 net/wireless/wext-sme.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
net/wireless/wext-sme.c +6 -2
index c67d7a82ab13..3fd2cc7fc36a 100644
@@ -201,6 +201,7 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 			       struct iw_request_info *info,
 			       struct iw_point *data, char *ssid)
 {
+	int ret = 0;
 	struct wireless_dev *wdev = dev->ieee80211_ptr;
 
 	/* call only for station! */

@@ -219,7 +220,10 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 		if (ie) {
 			data->flags = 1;
 			data->length = ie[1];
-			memcpy(ssid, ie + 2, data->length);
+			if (data->length > IW_ESSID_MAX_SIZE)
+				ret = -EINVAL;
+			else
+				memcpy(ssid, ie + 2, data->length);
 		}
 		rcu_read_unlock();
 	} else if (wdev->wext.connect.ssid && wdev->wext.connect.ssid_len) {

@@ -229,7 +233,7 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 	}
 	wdev_unlock(wdev);
 
-	return 0;
+	return ret;
 }
 
 int cfg80211_mgd_wext_siwap(struct net_device *dev,
Signature · 1 line
2.23.0.581.g78d2f28ef7-goog
Signature · 1 line
Kees Cook
Reviewed-by on v1 1/2
#3 lore raw
In reply to Will Deacon
Quoted 9 lines · Will Deacon

Although this shouldn't occur in practice, it's a good idea to bounds check the length field of the SSID element prior to using it for things like allocations or memcpy operations.

Cc <[email protected]>
Cc Johannes Berg <[email protected]>
Cc Kees Cook <[email protected]>
Reported-by Nicolas Waisman <[email protected]>
Signed-off-by Will Deacon <[email protected]>
Reviewed-by Kees Cook <[email protected]>

-Kees

Quoted 30 lines
---
 net/mac80211/mlme.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
net/mac80211/mlme.c +3 -2
index 26a2f49208b6..54dd8849d1cc 100644
@@ -2633,7 +2633,8 @@ struct sk_buff *ieee80211_ap_probereq_get(struct ieee80211_hw *hw,
 
 	rcu_read_lock();
 	ssid = ieee80211_bss_get_ie(cbss, WLAN_EID_SSID);
-	if (WARN_ON_ONCE(ssid == NULL))
+	if (WARN_ONCE(!ssid || ssid[1] > IEEE80211_MAX_SSID_LEN,
+		      "invalid SSID element (len=%d)", ssid ? ssid[1] : -1))
 		ssid_len = 0;
 	else
 		ssid_len = ssid[1];

@@ -5233,7 +5234,7 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
 
 	rcu_read_lock();
 	ssidie = ieee80211_bss_get_ie(req->bss, WLAN_EID_SSID);
-	if (!ssidie) {
+	if (!ssidie || ssidie[1] > sizeof(assoc_data->ssid)) {
 		rcu_read_unlock();
 		kfree(assoc_data);
 		return -EINVAL;
Signature · 1 line
2.23.0.581.g78d2f28ef7-goog
Signature · 1 line
Kees Cook